Specifications
16
Choosing the Correct Speaker Cabinets
When choosing a speaker cabinet to use with your Hartke Kilo, there are many speci-
cations to consider (impedance, power handling, frequency response, etc). While most
specs are pretty straight forward, many people have diculty understanding imped-
ance. Basically, impedance is the amount of current that will ow through a speaker
at a certain voltage. It is measured in Ohms. The actual impedance of a speaker is not
constant across all frequencies. So, for convenience we use the term “nominal imped-
ance”, which refers to the impedance that a speaker presents to an amplier at a refer-
ence frequency.
A typical speaker has an impedance rating of 4, 8, or 16 Ohms. Generally, the lower the
impedance of a speaker, the more power will be developed by a given amplier. For
example, a 4 Ohm speaker will extract more power from your amplier than an 8 Ohm
speaker. If you connect a speaker with an impedance lower than the rating of the am-
plier’s output, the amplier can overheat and damage the power output section. It is
important to learn how to connect multiple speaker cabinets safely without damaging
the speakers or the amplier in this way.
As a general rule, amplier speaker output jacks and speaker cabinet input jacks are
considered “parallel” connections, and will follow the rules described in this section.
When speakers are connected in parallel, the impedance is reduced. The formula to
calculate the total impedance of your speaker system is:
1/R
t
= 1/R
1
+ 1/R
2
+ 1/R
3
+ … 1/R
n
. Where “R” is the impedance of a speaker cabinet.
If all speakers have the same impedance, the total impedance will be equal to the
impedance of a single speaker divided by the total number of speakers. For example, if
you have two 4 Ohm speakers connected in parallel, the total impedance is 4 divided
by 2, or 2 Ohms. You must be careful when connecting speakers in parallel to an
amplier. The impedance can quickly fall below safe levels. This is especially true when
connecting speakers in parallel to a bridged amplier.
The Hartke Kilo has two independent ampliers capable of 500 watts, to which you
can connect speakers with a minimum impedance of 2 Ohms. The ampliers can be
bridged together to deliver 1000 watts of power to a minimum 4 Ohm speaker load.
When choosing speakers, make sure that they can match or exceed the output
power of the amplier, or you can damage the speakers.
16Ω + 16Ω = 8Ω
8Ω + 16Ω = 5.3Ω
8Ω + 8Ω = 4Ω
8Ω + 16Ω + 16Ω = 4Ω
16Ω + 16Ω + 16Ω + 16Ω = 4Ω
4Ω + 8Ω = 2.7Ω
4Ω + 4Ω = 2Ω
Typical Impedance Calculations